Are the estimated needs for mental health care among adolescents from different socioeconomic backgrounds met equally in Sweden? A longitudinal survey-registry linkage study

Evidence of inequality in the utilisation of mental health care (MHC) by adolescents in Nordic countries is mixed. This study aims to investigate if there are socioeconomic differences in the utilisation of MHC, while accounting for adolescents' mental health status. We analysed a cohort of 3517 adolescents, followed from 7 to 9th grade (ages 13-16), to examine the association between parental socioeconomic position (SEP: education and disposable income), adolescents' estimated needs, and the utilisation of MHC (defined as visits to secondary psychiatric care or receipt of psychotropic medication). Logistic and negative binomial regression models, with mental health status as moderator, were used to predict utilisation during each grade. Lower SEP predicted higher odds of utilising MHC in adolescents with no/mild symptoms (e.g., odds ratio, OR = 1.33, 95% CI 1.04-1.72, lower vs highest education), but not in those with moderate-to-severe symptoms (estimates close to one and non-significant). This pattern was largely explained by treatment of attention deficit hyperactivity disorder/autism spectrum disorders (ADHD/ASD) in boys. For girls with severe symptoms, lower SEP predicted reduced odds of utilising MHC for other mental disorders (OR = 0.48, 95% CI 0.25-0.92, lower education), and fewer outpatient visits when in contact with such care, although non-significant (incidence rate ratio, IRR = 0.51, 95% CI 0.25-1.05, lowest vs highest income). Our findings suggest a more equitable use of MHC for treating ADHD/ASD, but not other mental disorders such as depression and anxiety, particularly among girls.

Sirt2 promotes white matter oligodendrogenesis during development and in models of neonatal hypoxia

Delayed oligodendrocyte (OL) maturation caused by hypoxia (Hx)-induced neonatal brain injury results in hypomyelination and leads to neurological disabilities. Previously, we characterized Sirt1 as a crucial regulator of OL progenitor cell (OPC) proliferation in response to Hx. We now identify Sirt2 as a critical promoter of OL differentiation during both normal white matter development and in a mouse model of Hx. Importantly, we find that Hx reduces Sirt2 expression in mature OLs and that Sirt2 overexpression in OPCs restores mature OL populations. Reduced numbers of Sirt2+ OLs were also observed in the white matter of preterm human infants. We show that Sirt2 interacts with p27Kip1/FoxO1, p21Cip1/Cdk4, and Cdk5 pathways, and that these interactions are altered by Hx. Furthermore, Hx induces nuclear translocation of Sirt2 in OPCs where it binds several genomic targets. Overall, these results indicate that a balance of Sirt1 and Sirt2 activity is required for developmental oligodendrogenesis, and that these proteins represent potential targets for promoting repair following white matter injury.

Epidermal Growth Factor Receptor Inhibition Reverses Cellular and Transcriptomic Alterations Induced by Hypoxia in the Neonatal Piglet Brain

Acute hypoxia (HX) causes extensive cellular damage in the developing human cerebral cortex. We found increased expression of activated-EGFR in affected cortical areas of neonates with HX and investigated its functional role in the piglet, which displays a highly evolved, gyrencephalic brain, with a human-like maturation pattern. In the piglet, HX-induced activation of EGFR and Ca²⁺/calmodulin kinase IV (CaMKIV) caused cell death and pathological alterations in neurons and glia. EGFR blockade inhibited CaMKIV activation, attenuated neuronal loss, increased oligodendrocyte proliferation, and reversed HX-induced astrogliosis. We performed for the first time high-throughput transcriptomic analysis of the piglet cortex to define molecular responses to HX and to uncover genes specifically involved in EGFR signaling in piglet and human brain injury. Our results indicate that specific molecular responses modulated by EGFR may be targeted as a therapeutic strategy for HX injury in the neonatal brain.

Environmental enrichment ameliorates perinatal brain injury and promotes functional white matter recovery

Hypoxic damage to the developing brain due to preterm birth causes many anatomical changes, including damage to the periventricular white matter. This results in the loss of glial cells, significant disruptions in myelination, and thereby cognitive and behavioral disabilities seen throughout life. Encouragingly, these neurological morbidities can be improved by environmental factors; however, the underlying cellular mechanisms remain unknown. We found that early and continuous environmental enrichment selectively enhances endogenous repair of the developing white matter by promoting oligodendroglial maturation, myelination, and functional recovery after perinatal brain injury. These effects require increased exposure to socialization, physical activity, and cognitive enhancement of surroundings-a complete enriched environment. Using RNA-sequencing, we identified oligodendroglial-specific responses to hypoxic brain injury, and uncovered molecular mechanisms involved in enrichment-induced recovery. Together, these results indicate that myelin plasticity induced by modulation of the neonatal environment can be targeted as a therapeutic strategy for preterm birth.

Neighborhood Socioeconomic Characteristics and Utilization of ADHD Medication in Schoolchildren: A Population Multilevel Study in Stockholm County

Objective: To examine the effects of neighborhood socioeconomic disadvantage and ethnic composition on the utilization of ADHD medication in schoolchildren after accounting for individual- and family-level characteristics. Method: A cohort of all schoolchildren living in Stockholm County was prospectively followed for new prescriptions of ADHD medication (N = 276,955). Three-level logistic regression models were used with individual/family characteristics (e.g., immigrant background) at the first level and small area market statistics (SAMS) and municipality characteristics (i.e., socioeconomic disadvantage and ethnic composition) at the second and third level. Results: SAMS socioeconomic disadvantage was associated with increased utilization of ADHD medication. The utilization of ADHD medication was lower among immigrant children as compared with natives, and their odds of not utilizing medication increased as the degree of concentration of foreign-born increased. Conclusion: These results suggest that interventions at the neighborhood level may offer an additional route for the prevention of the disorder and/or alleviation of its consequences.

Has the association between low school performance and the risk of disability benefit due to mental disorders become stronger over time?

BACKGROUND

The proportion of young adults on disability benefits due to mental disorders has increased in Europe since the early 2000's. Poor educational achievement is a risk factor for disability benefits due to mental disorders in early adulthood, yet no study has examined whether this association has become stronger over time.

METHODS

All residents of Stockholm County at the time of graduation from compulsory education between 2000 and 2007 (N = 169,125) were followed prospectively for recipient of disability benefits due to a mental disorder from 2003 to 2011. Information about the study participants was obtained by linkage of national registers. Low school performance in the last year of compulsory school was defined as having a merit rating corresponding to the lowest quintile. The association between school performance and disability benefits was examined using Cox proportional hazards models.

RESULTS

Low school performers had a greater risk of disability benefits due to mental disorders during early adulthood, as compared to their better performing counterparts, and this association was more pronounced for the more recent graduation cohorts (OR = 1.12, 95% CI 1.08-1.16).

CONCLUSIONS

The association between low school performance and the risk of disability benefits due to mental disorders seems to become stronger during the first decade of the twenty-first century. It is plausible that this trend indicates an increased vulnerability of poor school performers to exclusion from the labor market. Prevention of school failure and adjustment of the labour market to individual variability in academic performance appear to be critical approaches to counteract this trend.

Cumulative exposure to childhood adversity, and treated attention deficit/hyperactivity disorder: a cohort study of 543 650 adolescents and young adults in Sweden

BACKGROUND

Though childhood adversity (CA) has been associated with the risk of attention deficit/hyperactivity disorder (ADHD), little is known about the effect of cumulative CAs and whether there are clusters of CAs that are more closely related with ADHD.

METHODS

We used a Swedish cohort of 543 650 individuals born 1987-1991. Register-based CAs included familial death, substantial parental substance abuse and psychiatric disorder, substantial parental criminality, parental separation, household public assistance recipiency, and residential instability. Individuals were followed from year 2006 when they were 15-19 years of age, for treated ADHD, defined as a registered ICD diagnosis and/or prescription of medications to treat ADHD. Logistic regression analysis was used to calculate odds ratios (OR) with 95% confidence intervals (CI). Latent Class Analyses (LCA) were used to identify clusters based on the different CAs.

RESULTS

All CAs increased the odds of ADHD in late adolescence and early adulthood; ORs ranged from 1.6 (95% CI 1.5-1.8) for familial death to 2.7 (95% CI 2.6-2.9) for household public assistance. We found a dose-response relationship between cumulative CA and ADHD; individuals with 4+ CAs had a markedly increased risk for ADHD (OR 5.5, 95% CI 5.0-6.0). LCA analyses revealed six distinct classes of CA associated with ADHD, of which 'exposure to most adversities' entailed highest risk.

CONCLUSION

CA is a strong risk factor for ADHD, particularly when accumulated. Early and efficient detection of CA is of importance for interventions targeted to improve long-term mental health outcomes among disadvantaged children.

The assessment of serum concentration of adiponectin, leptin and serum carbohydrate antigen-19.9 in patients with pancreatic cancer and chronic pancreatitis

Pancreatic cancer and chronic pancreatitis are still significant diagnostic and clinical problems. The clinical impact of preoperative serum carbohydrate antygen 19-9 (CA 19-9) levels have been disscussed. The aim of this study was a comparative analysis of the concentrations in serum of adipocytokines: adiponectin and leptin and CA 19-9 in patients with pancreatic cancer (PC), chronic pancreatitis (CP) and control group (CG). The study was performed in a group of 90 patients. Group 1 consisted of 30 patients with PC, group 2 consisted of 30 patients with CP. There was no coincidence of pancreatic cancer in CP group. Group 3 (CG) consisted of 30 persons and were recruited among patients operated for cholelithiasis. The serum samples were taken from patients and the concentration of adiponectin, leptin, CA 19-9 and CEA were evaluated. The revealed concentrations levels of the adiponectin were significantly higher in the PC serum samples compared to the CP and CG. There was no significant correlation between increased adiponectin concentration and body fat mass in the PC group. The concentration of leptin was significantly lower in CP serum samples compared to PC and CG. The concentration of leptin was similar in the PC and CG. The concentration of leptin was mainly dependent on body fat mass and fat distribution. Additionally, measurement of waist circumference and body composition was recorded using bioelectrical impedance analysis.

CONCLUSIONS

significantly higher concentration levels of adiponectin in the PC group, independent of body fat mass, may play a potential role as a new tumor marker in PC and might be useful in the differential diagnosis between PC and CP, but this statement needs further investigation. To our knowledge, this was the first study evaluating not only body mass index but also the content and distribution of body fat in patients with PC and CP.

Intranasal epidermal growth factor treatment rescues neonatal brain injury

There are no clinically relevant treatments available that improve function in the growing population of very preterm infants (less than 32 weeks' gestation) with neonatal brain injury. Diffuse white matter injury (DWMI) is a common finding in these children and results in chronic neurodevelopmental impairments. As shown recently, failure in oligodendrocyte progenitor cell maturation contributes to DWMI. We demonstrated previously that the epidermal growth factor receptor (EGFR) has an important role in oligodendrocyte development. Here we examine whether enhanced EGFR signalling stimulates the endogenous response of EGFR-expressing progenitor cells during a critical period after brain injury, and promotes cellular and behavioural recovery in the developing brain. Using an established mouse model of very preterm brain injury, we demonstrate that selective overexpression of human EGFR in oligodendrocyte lineage cells or the administration of intranasal heparin-binding EGF immediately after injury decreases oligodendroglia death, enhances generation of new oligodendrocytes from progenitor cells and promotes functional recovery. Furthermore, these interventions diminish ultrastructural abnormalities and alleviate behavioural deficits on white-matter-specific paradigms. Inhibition of EGFR signalling with a molecularly targeted agent used for cancer therapy demonstrates that EGFR activation is an important contributor to oligodendrocyte regeneration and functional recovery after DWMI. Thus, our study provides direct evidence that targeting EGFR in oligodendrocyte progenitor cells at a specific time after injury is clinically feasible and potentially applicable to the treatment of premature children with white matter injury.

Concentrations and activities of metalloproteinases 2 and 9 and their inhibitors (TIMPS) in chronic pancreatitis and pancreatic adenocarcinoma

Pancreatic cancer (PC) and chronic pancreatitis (CP) are still significant problems. The aim of this study was a comparative analysis of the activity and concentrations of matrix metalloproteinases 2 and 9 and the concentrations of their tissue inhibitors (TIMP 1 and 2) in the PC compared to CP tissue homogenates. The study was performed in a group of 63 patients with pancreatic cancer or chronic pancreatitis selected for resection procedures. Group 1 consisted of 31 patients with CP, group 2 consisted of 32 patients with PC. There was no coincidence of pancreatic cancer in CP group. The pancreatic tumor samples have been properly prepared in order to perform electrophoresis and immunoassay testing. The activity of MMPs and the concentrations of MMPs and TIMPs were evaluated.

RESULTS

the revealed activities of gelatinases and concentrations levels of the gelatinases and their inhibitors were significantly higher in the PC tissue samples compared to CP. In both groups, higher concentrations of MMP9 compared to MMP2 and TIMP2 compared to TIMP1 were shown. High potential for tumor invasiveness demonstrated by the formation of lymph node metastases was characterized by the higher concentrations of MMP9 and TIMP2. However, in the case of infiltration of the nerve fibers, a decrease in the concentration of MMP2 was found.

CONCLUSIONS

gelatinases and their inhibitors play important role in the pathogenesis of the CP as well as PC. The activity and concentration of gelatinases and the concentration of their inhibitors were all significantly higher in the PC group.

Pain among women: Associations with socio-economic and work conditions

We examined pain prevalence (general/body sites) and its characteristics/consequences among a randomised sample of women from the general population between 18 and 64 years (n=3,616). We also scrutinised associations between pain and various factors (e.g. socio-economic) by means of multivariate logistic/linear regression analyses. The women completed a questionnaire assessing various areas (e.g. pain). The design was cross-sectional and data were collected during 8 consecutive weeks. Sixty-three per cent of women reported pain during the last 3 months, of which 65% during more than 3 months. The multivariate analyses revealed associations between various socio-economic factors (e.g. financial strain) and pain in general/all studied body sites. In addition, psychosocial work conditions (i.e. work strain and social support) were significantly related to pain. Moreover, the multivariate analyses conducted among women with pain indicated relationships between socio-economic/psychosocial work conditions, and pain characteristics (e.g. intensity) and consequences (i.e. disability). A large number of women from the general population suffer from pain, in particularly prolonged pain. Women in a deprived socio-economic situation not only run a higher pain risk, but also experience their pain as more severe/disabling than their more privileged counterparts. Improvements of, for example, the socio-economic status among women living in deprived social and material circumstances, along with improved working environment may be crucial to reduce women's pain problems.

A national cohort study of parental socioeconomic status and non-fatal suicidal behaviour--the mediating role of school performance

BACKGROUND

A link between low parental socioeconomic status and mental health problems in offspring is well established in previous research. The mechanisms that explain this link are largely unknown. The present study investigated whether school performance was a mediating and/or moderating factor in the path between parental socioeconomic status and the risk of hospital admission for non-fatal suicidal behaviour.

METHODS

A national cohort of 447 929 children born during 1973-1977 was followed prospectively in the National Patient Discharge Register from the end of their ninth and final year of compulsory school until 2001. Multivariate Cox proportional hazards and linear regression analyses were performed to test whether the association between parental socioeconomic status and non-fatal suicidal behaviour was mediated or moderated by school performance.

RESULTS

The results of a series of multiple regression analyses, adjusted for demographic variables, revealed that school performance was as an important mediator in the relationship between parental socioeconomic status and risk of non-fatal suicidal behaviour, accounting for 60% of the variance. The hypothesized moderation of parental socioeconomic status-non-fatal suicidal behaviour relationship by school performance was not supported.

CONCLUSIONS

School performance is an important mediator through which parental socioeconomic status translates into a risk for non-fatal suicidal behaviour. Prevention efforts aimed to reduce socioeconomic inequalities in non-fatal suicidal behaviour among young people will need to consider socioeconomic inequalities in school performance.

Psychosocial experiences among primary care patients with and without musculoskeletal pain

We examined differences in demographic/financial characteristics, burnout, job demands/control/strain and symptoms of depression as measured by GHQ among primary care patients with (n=838) and without pain (n=135). In addition, we examined factors associated with the presence of pain by means of logistic regression analyses among all participants, and inter-relations between demographic/financial/pain/health variables, symptoms of depression, burnout, and disability by means of multivariate regression analyses among pain patients. The patients completed a questionnaire about areas such as job strain and burnout. The design was cross-sectional and data were collected during 15 consecutive days. The univariate analyses showed that pain patients, compared with patients without pain, were more often females, older, divorced, foreign-born, had been more often on sick-leave, were more preoccupied with how to make ends meet and had greater difficulties in raising a reasonable sum of money within a specific period of time. In addition, they had greater levels of depression symptoms, burnout, and job strain. However, the multivariate analyses showed that symptoms of depression and burnout were more associated with such variables as sick-leave and divorce than by pain parameters. The logistic regression revealed that the presence of pain was associated with female gender, sick-leave, and high levels of job strain and mean total burnout. Finally, pain patients had a severe clinical situation in terms of, for example, constant, intense, and prolonged pain, and experienced a high degree of disability due to pain. We corroborated previous findings and may have provided new insights into the experiences of pain patients that may be of importance when considering intervention. Although we pointed to some important factors associated with pain, symptoms of depression and burnout, much of their variation remains to be explained. Thus, further research appears necessary, not least concerning the role of burnout as an antecedent to pain.

Cdk2 loss accelerates precursor differentiation and remyelination in the adult central nervous system

Cdk2 is not essential for oligodendrocyte maturation and myelination during development, but in response to demyelination, it is required for oligodendrocyte precursor cell proliferation (OPC), and its loss accelerates OPC differentiation and remyelination.

The specific functions of intrinsic regulators of oligodendrocyte progenitor cell (OPC) division are poorly understood. Type 2 cyclin-dependent kinase (Cdk2) controls cell cycle progression of OPCs, but whether it acts during myelination and repair of demyelinating lesions remains unexplored. Here, we took advantage of a viable Cdk2^−/− mutant mouse to investigate the function of this cell cycle regulator in OPC proliferation and differentiation in normal and pathological conditions. During central nervous system (CNS) development, Cdk2 loss does not affect OPC cell cycle, oligodendrocyte cell numbers, or myelination. However, in response to CNS demyelination, it clearly alters adult OPC renewal, cell cycle exit, and differentiation. Importantly, Cdk2 loss accelerates CNS remyelination of demyelinated axons. Thus, Cdk2 is dispensable for myelination but is important for adult OPC renewal, and could be one of the underlying mechanisms that drive adult progenitors to differentiate and thus regenerate myelin.

School performance and hospital admissions due to self-inflicted injury: a Swedish national cohort study

BACKGROUND

Self-inflicted injury in youth has increased in many Western countries during recent decades. Education is the most influential societal determinant of living conditions in young people after early childhood. This study tested the hypothesis that school performance predicts self-inflicted injury.

METHODS

A national cohort of 447 929 children born during 1973-77 was followed prospectively in the National Patient Discharge Register from the end of their ninth and last year of compulsory school until 2001. Multivariate Cox analyses of proportional hazards were used to test hypotheses regarding grades in ninth grade as predictors of hospital admission due to self-inflicted injury.

RESULTS

The risk of hospital admission because of self-inflicted injury increased steeply in a step-wise manner with decreasing grade point average. Hazard ratios were 6.2 (95% confidence interval 5.5-7.0) in those with the lowest level of grade point average compared with the highest. The risks were similar for women and men. Adjustment for potential socio-economic confounders in a multivariate proportional hazards regression analysis attenuated this strong gradient only marginally.

CONCLUSION

School performance is a strong factor for predicting future mental ill-health as expressed by self-inflicted injury.

Ethnicity, socio-economic status and self-harm in Swedish youth: a national cohort study

BACKGROUND

Previous studies have shown an elevated risk for self-harm in adolescents from ethnic minorities. However, potential contributions to this risk from socio-economic factors have rarely been addressed. The main aim of this article was to investigate any such effects.

METHOD

A national cohort of 1009 157 children born during 1973-1982 was followed prospectively from 1991 to 2002 in Swedish national registers. Multivariate Cox analyses of proportional hazards were used to estimate the relative risk of hospital admission for self-harm. Parental country/region of birth was used as proxy for ethnicity.

RESULTS

Youth with two parents born outside Sweden (except those from Southern Europe) had higher age- and gender-adjusted hazard ratios (HRs) of self-harm than the majority population (HR 1.6-2.3). The HRs decreased for all immigrant groups when socio-economic factors were accounted for but remained significantly higher for immigrants from Finland and Western countries and for youth with one Swedish-born and one foreign-born parent.

CONCLUSIONS

Socio-economic factors explain much of the variation by parental country of birth of hospital admissions for self-harm in youth in Sweden.

Cdk2 is critical for proliferation and self-renewal of neural progenitor cells in the adult subventricular zone

We investigated the function of cyclin-dependent kinase 2 (Cdk2) in neural progenitor cells during postnatal development. Chondroitin sulfate proteoglycan (NG2)–expressing progenitor cells of the subventricular zone (SVZ) show no significant difference in density and proliferation between Cdk2^−/− and wild-type mice at perinatal ages and are reduced only in adult Cdk2^−/− mice. Adult Cdk2^−/− SVZ cells in culture display decreased self-renewal capacity and enhanced differentiation. Compensatory mechanisms in perinatal Cdk2^−/− SVZ cells, which persist until postnatal day 15, involve increased Cdk4 expression that results in retinoblastoma protein inactivation. A subsequent decline in Cdk4 activity to wild-type levels in postnatal day 28 Cdk2^−/− cells coincides with lower NG2⁺ proliferation and self-renewal capacity similar to adult levels. Cdk4 silencing in perinatal Cdk2^−/− SVZ cells abolishes Cdk4 up-regulation and reduces cell proliferation and self- renewal to adult levels. Conversely, Cdk4 overexpression in adult SVZ cells restores proliferative capacity to wild-type levels. Thus, although Cdk2 is functionally redundant in perinatal SVZ, it is important for adult progenitor cell proliferation and self-renewal through age-dependent regulation of Cdk4.

Risk behaviours, victimisation and mental distress among adolescents in different family structures

BACKGROUND

Previous studies have shown an elevated risk with regard to social and behavioural domains in adolescents of single parents. However, the diversity of single parent families concerning gender of the resident parent has seldom been taken into account when investigating the relation between family structure and children's negative outcomes. Thus, the aim of this study was to investigate risk behaviours, victimisation and mental distress among adolescents in different family structures using more detailed sub-groups of single parents (i.e., single mother, single father and shared physical custody).

METHODS

The sample consisted of 15,428 ninth graders from all municipal and private schools in the county of Stockholm (response rate 83.4%). Risk behaviours included use of alcohol, illicit drugs and smoking. Victimisation was measured by experiences of exposure to bullying and physical violence. Mental distress was assessed with the anxious/depressed and aggressive behaviour syndrome scales in the Youth Self Report (YSR). Bivariate and multivariate logistic regression analyses were used to investigate the associations between family structure and outcome variables.

RESULTS

Adolescents in single-mother/father families were at higher risk of risk behaviours, victimisation and mental distress than their counterparts in two-parent families. However, after control for possible confounders the associations between victimisation, aggressive behaviour problems and single motherhood were no longer significant, whereas these relations remained for children living with single fathers. Adolescents in shared physical custody run no increased risk of any of the studied outcomes (except drunkenness) after adjustment for covariates. Post hoc analyses revealed that adolescents in single-father families were at higher risk for use of alcohol, illicit drugs, drunkenness, and aggressive behaviour as compared to their peers in single-mother families, whereas no differences were found between adolescents in single-mother families and those in shared physical custody.

CONCLUSIONS

Children of single parents should not be treated as a homogenous group when planning prevention and intervention programmes. Researchers and professionals should be aware of and consider the specific problems of single parent children and that their problems may vary depending on their living arrangements.

Alteration of interneuron migration in a ferret model of cortical dysplasia

During cerebral cortical development, gamma-aminobutyric acidergic (GABAergic) interneurons arise from a different site than projection neurons. GABAergic cells are generated in the subpallial ganglionic eminence (GE), while excitatory projection neurons arise from the neocortical ventricular zone. Our laboratory studies a model of cortical dysplasia that displays specific disruption of GABAergic mechanisms and an alteration in the overall balance of excitation in the neocortex. To produce this model, the birth of neurons on a specific gestational day in ferrets (embryonic day 33 [E33]) is interrupted by injection of the antimitotic methylazoxymethanol (MAM). We hypothesized that migration of interneurons might be disrupted in this cortical dysplasia paradigm. We observed that although interneurons migrate into the neocortex in both normal and dysplastic cortex, the migrating cells become disoriented over time after E33 MAM treatment. Coculture experiments using normal GE and MAM-treated cortex (and vice versa) demonstrate that cues dictating proper orientation of migrating interneurons arise from the cortex and are not intrinsic to the migrating cells. As a consequence, interneurons in mature brains of MAM-treated animals are abnormally distributed. We report that GABA(A) receptor activation is crucial to the proper positioning of interneurons migrating into the cortex from the GE in normal and MAM-treated animals.

The growth capacity of bone marrow CD34 positive cells in culture is drastically reduced in a murine model of Down syndrome

Human trisomy 21, Down syndrome (DS), is characterized by mental retardation. In addition, high risks of developing hematological and immune disorders, as well as cardiac, skeletal and other abnormalities are life-long concerns. Recent data suggested that bone marrow contains progenitors, hematopoietic or stromal cells, which may have the potential of generating non hematopoietic tissue such as neural cells, cardiac cells or osteoblasts. Therefore we have used a model of Down syndrome, Ts65Dn mice, to investigate their bone marrow. We have found that the vast majority of CD34(+) cells in the bone marrow of adult Ts65Dn mice, but not of the CD34(-) cells, exhibit a drastic reduction in their in vitro growth capacity. In addition to neural antigens, cultured CD34(+) cells from trisomic and diploid mice also expressed mast cell markers.

GABAA Receptors Reorganize when Layer 4 in Ferret Somatosensory Cortex is Disrupted by Methylazoxymethanol (MAM)

We established a model of cortical development that arrests the birth of layer 4 cells by injecting methylazoxymethanol (MAM) on embryonic day 33 (E33) in ferrets. This leads to adult somatosensory cortex with a very thin layer 4. Earlier, we determined the relative absence of layer 4 changed the growth and differentiation of the somatosensory cortex and the growth of thalamic afferents into the cortical plate. To identify other features of cortical organization that might be altered after MAM treatment, we assessed the distribution of selected excitatory and inhibitory receptors in area 3b of ferret somatosensory cortex. Initial screening revealed the distribution of several excitatory receptors (NMDA, AMPA, kainate) in E33 MAM-treated cortex was similar to that in normal adult animals. In contrast, the binding pattern of inhibitory GABAA receptors was altered in MAM-treated cortex. Normally, GABAA receptors densely locate in central layers of cortex. In E33 MAM-treated animals, GABAA receptor binding extended superficially, covering a broader area of cortex. Further experiments using antibodies directed against GABAAalpha receptors disclosed that pan alpha GABAA receptors strongly localize to layer 4 in normal area 3b. In E33 MAM-treated cortex, however, GABAAalpha receptors extend outside and are located above and below the very thin layer 4. The redistribution of inhibitory receptors suggests that layer 4 plays an important role in regulating thalamic terminations and also in the resulting ability to refine processing of incoming stimuli.

A radialization factor in normal cortical plate restores disorganized radial glia and disrupted migration in a model of cortical dysplasia

Treatment of pregnant ferrets on embryonic day 24 (E24) with the antimitotic methylazoxy methanol (MAM) leads to a specific constellation of effects in newborn kits, which include a very thin and poorly laminated neocortex, disruption of radial glial cell morphology with early differentiation into astrocytes, and abnormal positioning of Cajal-Retzius cells. We suggest that MAM treatment on E24 results in this model of cortical dysplasia by eliminating a population of cells that produce a factor capable of maintaining radial glia in their normal morphology. The abnormal radial glia, either alone or in combination with other abnormal features, are likely to prevent proper migration into the cortical plate. To test the possibility that normal cortex can provide the missing substance that influences radial glia, slices of E24 MAM-treated cortex were removed at postnatal day 0 (P0) and cultured adjacent to explants of P0 normal cortical plate. By labelling a small number of cells with injections of fluorescent dextrans into the cultured slices, we found that abnormal radial glia in MAM treated slices cocultured adjacent to normal cortical plate were restored toward normal, in comparison to E24 MAM treated slices cultured alone and in other control conditions. We also found that abnormally positioned Cajal-Retzius cells move into the marginal zone and that neurons are able to migrate into the cortical plate more effectively in the coculture condition. These data indicate that normal cortical plate of ferrets contains a factor causing radial glia to maintain their elongated morphology; the improved position of radial glia encourages repositioning of Cajal-Retzius cells and improved neuronal migration into the cortical plate.

Rapid regulation of GAD67 mRNA and protein level in cortical neurons after sensory learning

Cortical representations of different modalities can be modified by sensory learning. Our previous studies in the barrel cortex showed that expansion of the cortical representation of a row of vibrissae could be induced by pairing stimulation of a row of vibrissae with a tail shock. The plastic change in cortical reactivity to the input used during the training was accompanied by increased density of GABA immunoreactive neurons in the involved row of cortical barrels. Using the same paradigm, the present study examined the pathway of GABA synthesis-expression of GAD67 mRNA and immunoreactivity of GAD67 isoenzyme in the barrel cortex of mice after sensory learning. In situ hybridization revealed that the GAD67 mRNA level was elevated in one row of barrels in the trained group as well as in controls receiving vibrissae stimulation alone. In contrast, elevation of immunoreactivity of the GAD67 protein occurred only in the trained group. The density of GABA-immunoreactive neurons in the hollows of barrels representing the row of vibrissae activated during the training was increased by 50%. These data indicated that sensory stimulation alone affected expression of the 67 kDa glutamate decarboxylase isoenzyme synthesis pathway, whereas the processes involved in cortical plasticity induced by associative learning modified this pathway additionally at the level of translation.

Laminar specific alterations of thalamocortical projections in organotypic cultures following layer 4 disruption in ferret somatosensory cortex

The developing neocortex influences the growth of thalamocortical projections. Layer 4 in particular receives the majority of input from the thalamus and is important in instructing thalamic afferents to terminate. Previous in vivo experiments demonstrated that disruption of layer 4 during corticogenesis in ferret somatosensory cortex by application of methylazoxy methanol acetate (MAM) prevents proper termination of thalamic afferents in appropriate cortical regions. To further explore the role of layer 4 in thalamocortical development, we prepared organotypic cocultures consisting of normal gestational day 0 (P0) ferret thalamus paired with normal, embryonic day 33 (E33), or E38 MAM-treated cortex obtained from ferrets at either P0 or P7. Injection of MAM on E33 disrupts layer 4 formation, whereas similar injections on E38 interfere with layer 2 formation. The cocultures grew together for a number of days, then discrete injections of either fluorescent dextrans or 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI) were made into the thalamic piece. The labeled thalamic afferents that grew into the cortical slice were analysed and the sites of their terminations quantified after 3, 5, or 7-10 days in culture (DIC). Our results varied somewhat with the amount of time in culture, but the preponderance of thalamic fibers in normal cortex terminated in layer 4, whereas their counterparts in E33 MAM-treated cortex grew beyond the cortical plate and many fibers terminated inappropriately within lower cortical layers or white matter. Terminal distribution of thalamic fibers in E38 MAM-treated cortex looked similar to normal. These results demonstrate that the cells of layer 4 provide thalamic afferents with important positional and termination cues.

Differences between rats and rabbits in NMDA receptor-mediated calcium signalling in hippocampal neurones

In vivo microdialysis combined with the measurement of (45)Ca(2+) efflux from prelabelled hippocampus demonstrated a pronounced N-methyl-D-aspartate (NMDA)-evoked (45)Ca(2+) release to the dialysate in the rat dentate gyrus (DG) and CA1, whereas in rabbit a slight release of (45)Ca(2+) was observed only in the DG. In vitro, we noticed that the NMDA-evoked increase in Fura-2 detected intracellular Ca(2+) concentration in synaptoneurosomes from the rat, but not from the rabbit hippocampus, was strongly inhibited by the ryanodine receptor (RyR) antagonists dantrolene and ryanodine. To establish the mechanism of these differences, we characterised their possible dependence on the expression of RyR and their co-localisation with the calcium binding protein calbindin D(28k). A pronounced expression of [(3)H]ryanodine binding sites in the rat DG, which is only slight in the CA1, was demonstrated whereas in rabbit they were only found in the DG. The pattern of expression of calbindin D(28k) immunoreactivity and RyR in the rat and rabbit hippocampus was similar. These results suggest that the functional role of RyR in the generation of the NMDA receptor-mediated intracellular Ca(2+) signalling in the rabbit hippocampal neurones is marginal when compared to the rat. These differences reflect a diverse expression of RyR in both species. The corresponding differences in calbindin D(28k) immunoreactivity are most probably secondary in nature.

NMDA-induced 45Ca release in the dentate gyrus of newborn rats: in vivo microdialysis study

This in vivo study, aimed at detecting the N-methyl-D-aspartate (NMDA) evoked Ca(2+)-induced Ca(2+) release from intracellular stores in the neonatal rat brain, demonstrates that the application of 5 mM N-methyl-D-aspartate via a microdialysis probe for 20 min to the dentate gyrus (DG) of halotane-anesthetized 7 day-old (postnatal day 7, PND 7) rats induces a prolonged decrease in Ca(2+) concentration in an initially calcium-free dialysis medium, indicative of a drop in the extracellular concentration of Ca(2+) and Ca(2+) influx to neurons. In parallel experiments, a huge NMDA-evoked release of 45Ca from the pre-labeled endogenous Ca(2+) pool was observed and interpreted as the expression of intracellular Ca(2+) release. Dantrolene (100 microM) significantly inhibited the NMDA-induced 45Ca release, whereas 250 microM ryanodine exerted an unspecific biphasic effect. Autoradiographic and immunocytochemical detection of ryanodine receptors and calbindin D(28K), respectively, in the hippocampal region of PND 7 rats displayed a pronounced expression of [3H]ryanodine binding sites in the DG, but only a slight immunoreactivity of calbindin D(28K). Plastic changes in neurons or excitotoxic neuronal damage induced by the activation of NMDA receptors are mediated by Ca(2+) signals, resulting from an influx of extracellular Ca(2+), and also in some neurons, from the release of intracellular Ca(2+). Our previous in vivo microdialysis experiments visualized NMDA-evoked 45Ca release in the adult rat dentate gyrus, attributable to Ca(2+)-induced Ca(2+) release from the ryanodine-sensitive pool. An additional role of calbindin in the mechanism of this phenomenon has been suggested. This aspect has not been studied in vivo in newborn rats. Our present results indicate that the release of 45Ca from the prelabeled intracellular, dantrolene-sensitive Ca(2+) pool in the DG neurons of immature rats, most probably representing a phenomenon of Ca(2+)-induced Ca(2+) release, significantly participates in the generation of NMDA receptor-mediated intracellular Ca(2+) signals, whereas the role of calbindin D(28K) in the mechanism of 45Ca release is negligible.

Deafferentation induced changes in GAD67 and GluR2 mRNA expression in mouse somatosensory cortex

Partial vibrissectomy in adult mice induces body map plasticity in SI barrel cortex. To examine if the disturbed balance of cortical activation affects the excitatory and inhibitory neurotransmitter systems, we studied glutamic acid decarboxylase (GAD 67) and AMPA receptor subunit GluR2 mRNA expression in the barrel cortex. At varying times post-vibrissectomy, sparing row C of whiskers on one side of the snout, the brains were processed for in situ hybridization using specific [(35)S]oligonucleotides to detect the laminar localization of GAD67 and GluR2 mRNAs. Three and seven days after vibrissectomy, the expression of GAD67 was decreased in the deafferented cortex, while 30 days post-lesion, no effects were observed. At 3 days post-lesion, an ipsilateral decrease in GAD67 mRNA expression was also observed. No decreases in GluR2 transcripts were found in the deafferented cortex, but an increased expression was observed in the representation of the spared row C of whiskers 3 days after vibrissectomy. Seven and 30 days post lesion no changes in GluR2 expression were found. These data indicate that in the barrel cortex, peripheral deafferentation transiently regulates GAD67 and GluR2 expression at the transcriptional level. We suggest that this may be a manifestation of adaptive processes.

Partial blocking of NMDA receptors reduces plastic changes induced by short-lasting classical conditioning in the SI barrel cortex of adult mice

The effect of blockade of N-methyl-D-aspartate (NMDA) receptors in the barrel cortex upon the learning-induced changes of the cortical body map was examined in adult mice. We have previously found that three sensory conditioning sessions, in which stimulation of a row of vibrissae was paired with a tail shock, produced an enlargement of the functional representation of a row of vibrissae stimulated during training. Implantation of the slow release polymer Elvax, containing 2-amino-5-phosphonovalerate (APV, 50 mM), in the vicinity of the barrel cortex was performed 1 day before conditioning to block NMDA receptors. The cortical representation of a trained row of vibrissae was visualized with 2-deoxyglucose (2DG) functional brain mapping 1 day after the completion of the conditioning procedure. The partial blockade of NMDA receptors within the barrel cortex reduced (by half) the expansion of the cortical representation of a trained row of vibrissae as compared to the enlargement of the cortical representation of a trained row found in untreated (60%) and Elvax-PBS implanted (47%) mice. The results provide evidence that the learning-induced processes of cortical map reorganization involve mechanisms that depend on NMDA receptor activation.